The invention relates to a resilient seal.
Since the introduction of highly resilient, pressure-energized metallic sealing rings, such as that according to U.S. Pat. No. 3,797,836, in the early 1970""s, temperatures and pressures in turbine engines, where such rings may be employed, have increased substantially. Increased operating temperatures and pressures have caused the magnitude of the displacements between cooperating members of sealing surfaces to correspondingly increase. These cooperating sealing surfaces must seal together, under all operating conditions, to contain, for example, working gases at temperatures up to 1800xc2x0 F. and cooling air at over 1200xc2x0 F.
One way to provide effective sealing for the increasingly large and variable displacement between cooperating members of sealing surfaces is by providing multiple convolutions between cantilever sealing members at each end of a sealing ring, as shown, for example, in U.S. Pat. No. 4,121,843. As displacement continued to increase, a further response was desired. This came in the form of multiple-ply sealing ring construction, in which the thinner plies, capable of containing the fluid under pressure, when used in layers, provided the capacity for up to two or more times the deflection at a given stress level compared to single-ply seals. U.S. Pat. Nos. 5,249,814 and 5,716,052 describe sealing rings using multiple-ply technology.
Multiple-ply sealing rings, such as that described in U.S. Pat. No. 5,249,814, can be expensive because, for example, a seal may be required to have its edges welded together to prevent the ingress of pressurized media between the plies, where such ingress would cause overstressing of the material of the ply at the greatest distance from the higher pressure source. Seals such as that disclosed in U.S. Pat. No. 5,716,052 overcame that cost barrier associated with use of multiple plies by folding over the edges at each end of the seal section. For illustration purposes, a cross-section of a seal 1000 according to U.S. Pat. No. 5,716,052, is depicted in FIG. 10. By folding over the edges 1002, 1004, 1006, and 1008 at each end of the seal 1000, so that the openings to the interstitial space 1010 between the plies 1012 and 1014 were exposed to the lower pressure zone instead of the higher pressure medium being sealed, the seal 1000 depicted in FIG. 10 prevented the ingress of pressurized media between the plies.
However, because each of the bends at the folded ends of seals, such as a seal depicted in FIG. 10, have two thicknesses of seal material for every ply of the seal, such seals had several disadvantages. Among the disadvantages were stiffness at the termination regions (i.e., the folded ends in the region of the seal""s sealing lines), where flexibility is needed; inactivity at the tightly folded edges of the seal, providing no flexibility to accommodate longitudinal axial displacement; and the consumption of critically necessary axial space.
A seal consisting of three plies, such as are described in U.S. Pat. No. 5,716,052 has six layers of material and three folds at each end.
In one aspect, a seal according to the present invention has a first surface, which may be, for example, a pressure-facing ply and a second surface, which may be, for example, a non-pressure-facing ply. The plies are joined at the free ends of the seal by leg termination regions. Leg termination regions form the rounded end portions of an interstitial space, which exists between the first and second surfaces, or plies.
In another aspect, the first surface is comprised of a convolution region, two acute bend regions, and two leg regions. The convolution region is comprised of a curved region, which can be any curved or compound curved shape (e.g., a partial circle or a partial ellipse) and two sidewall regions. Each sidewall region extends between the curved region and an adjoining acute bend region. The second surface is comprised of a convolution region, two acute bend regions, and two leg regions. The convolution region is comprised of a curved region, which can be any curved or compound curved shape (e.g., a partial circle or a partial ellipse) and two sidewall regions. Each sidewall region extends between the curved region and an adjoining acute bend region. The first surface and the second surface are joined by leg termination regions. The regions may form a unitary structure.
In other aspects, a seal according to the present invention may have at least one layer of material disposed between the first and second surfaces, or plies, of the seal. Such an inter-ply surface is substantially enveloped by the outer-most first and second surface plies. A seal according to the present invention may also be formed in multiple-convolutions, wherein the layers or plies of the seal may have substantially the same convoluted shape and are disposed, more or less, adjacent to each other.